1. Field of the Invention
This invention relates to the production of wide glassy alloy ribbons by chill block melt-spinning and in particular to the critical gas boundary layer Reynolds number above which wide glassy alloy ribbons with serrated edges and surface perforations result when cast at an impingement angle .alpha..
2. Description of the Prior Art
Relationships between processing parameters and dimensions of glassy alloy ribbons formed by melt-spinning have been discussed by Chen and Miller in Material Research Bulletin 11, 49 (1976), Liebermann and Graham, Jr., I.E.E.E. Transactions Mag-12, No. 6, 921(1976) and Kavesh, Metallic Glasses, ed. J.J. Gilman, A.S.M. (1978), Ch. 2. However, the nature of the gas boundary layer associated with the motion of the substrate wheel and its effects on the melt puddle and resultant ribbon geometry have not been quantitatively considered in the literature. Although relatively narrow glassy alloy ribbons may be cast satisfactorily without special care regarding the prevalent atmosphere in which melt-spinning is conducted, the fabrication of wider ribbons with good surface finish and smooth edge is found to be difficult or impossible without controlling the gas boundary layer on the circumferential surface of the rotating substrate wheel. Failure to control this boundary layer typically results in ribbons with serrated edges and possible longitudinal slits.
It is therefore an object of this invention to provide a new and improved method for processing wide glassy alloy ribbons.
Another object of this invention is to provide a new and improved method for processing glassy alloy ribbons wherein substantially higher than prior art substrate speeds are employed in the manufacture of very thin wide ribbons.
A further object of this invention is to provide a new and improved method for processing wide glassy alloy ribbons embodying a critical gas boundary layer Reynolds number for developing parameters when casting at an impingement angle .alpha..